In general, an electric discharge machine includes a machine body or machining unit having a machining gap formed between a tool electrode and a workpiece being machined, a power supply for supplying electric energy to the machining gap and a dielectric supply device for supplying a dielectric fluid, such as kerosine or water, to the machining gap. The power supply is necessarily positioned with a physical spacing from the machine body and connected to the machine body by means of appropriate conductors.
A train of successive voltage pulses from the power supply are applied across the machining gap to induce electric discharges across the machining gap so that a current starts to flow through the machining gap, thereby resulting in the machining of the workpiece.
It is well known to use a coaxial cable, which has an inner conductor and a conductive shield insulated from the inner-conductor, to reduce the undesirable self-inductance of the conductors connected between the power supply and the machine body. However, the stray capacitance between the inner-conductor and the shield adversely affects the quality of the machined surface of the workpiece particularly when a relatively long cable is used.